This invention relates to navigation aids and plotters or computers for small aircraft users, small boats, and similar vehicles where navigation by directional radio signals is desired without the availability of sufficient space for large detailed charts and the instruments necessary for their proper interpretation. The device disclosed herein eliminates the need for an air or sea chart to ascertain the magnetic heading and distance remaining at various intervals or points along a course from the starting point to a destination.
While this navigation aid can be used in conjunction with any type of cartographic charts, it is particularly useful in conjunction with the "Sectional Aeronautical Charts" published and printed by the U. S. Coast and Geodetic Survey Office of the Department of Commerce, which are almost universally used by private pilots in the U.S. On these charts, all airports are indicated by a legend and those having "Very High Frequency Omni-Directional Radio Range" (VOR) are indicated with an imprinted compass rose. The compass rose surrounds the airport on the chart and is aligned with magnetic North.
The angular and distance relationship between any two points on a chart can be readily determined by the use of mechanical plotting devices which typically comprise a circular compass rose and a longitudinal distance scale pivotally mounted about the center of the compass rose. Examples of such devices are illustrated in the prior patents to Sabadishin, U.S. Pat. No. 3,387,372, Haws, U.S. Pat. No. 3,881,253 and Price, U.S. Pat. No. 3,855,706.
Any intermediate navigational position can be plotted by determining the intersection of the signals received from two VOR stations. While various devices have been designed to assist in determining this intersection in an aircraft, they typically require pins be inserted through a chart, and require placement and manipulation of devices having two elongated arms and a pair of compass roses. An example is the apparatus shown in the Sabadishin U.S. Pat. No. 3,387,372 and the patent to Cherry, U.S. Pat. No. 3,824,693. More complicated instruments having two or more pivoted arms are illustrated in the following representative prior U.S. Pat. Nos. McCluskey, 2,159,562; Baumgartner, 2,448,410; Hart, 2,641,843; Greene, 2,736,096; Casagrande, 3,187,434; Preuit, 3,281,942; and Novakovic 3,621,578. While these devices mathematically locate navigational positions from charts, they all require the instrument to be used directly upon a reference chart. Most are more concerned with locating the position of the user with reference to radio signal locators, and require substantial manipulation to determine a heading to a destination other than a position having a VOR station.
In contrast, the present device, while preset by reference to a chart, requires no chart during normal use while flying an aircraft or operating a boat. It serves to directly compute the heading required to reach any intermediate destination and simultaneously provides a visual indication of the distance from the present position of the user to the desired destination. Because it does not have to be used while resting on a chart, it can be constructed to a relatively small scale so as to be mounted in a cockpit without interferring with other instruments or with the vision of the user. Its manipulation and setting is relatively easy, and it readily provides the user with information otherwise available only through much more expensive sophisticated radio navigational equipment commonly found in commercial aircraft.